Level shifters receive a signal relative to a low supply voltage and a high supply voltage and produces an output signal similar to the received signal except that the output signal is relative to a second low supply voltage and a second high supply voltage. For example, a level shifter can receive a digital signal which swings between 0V and 3.3V and produce a digital output signal with the same high and low values except that the high value is 5V and the low value is 1.7V.
Level shifters can be employed in a wide variety of applications. They are used in class-D amplifier by amplifying the swing of a square wave form. They can be used in DC-DC power converters. Also, they can be used in interface circuits between different circuits which use different high or low reference voltages.